import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int a = in.nextInt();
            int b = in.nextInt();
            int count = 0;
            for(int i = a; i <= b; i++) {
                count += Frequency(i);
            }
            System.out.println(count);
        }
    }
    public static int Frequency(int n) {
        int count = 0;
        while(n > 0) {
            if(n % 10 == 2) {
                count++;
            }
            n = n / 10;
        }
        return count;
    }
}